1. Field of Invention
The present invention relates generally to networks. More particularly, the present invention relates to a multi-functional dense wave division multiplexing line card that has add/drop multiplexer, transponder, and muxponder capabilities, and may be readily reconfigured to support additional traffic demands.
2. Description of the Related Art
The use of the Gigabit Ethernet (GbE) communications protocol is becoming more widely used in networking applications. As a result, synchronous optical network (SONET) or synchronous digital hierarchy (SDH) networks that were not designed to transport GbE signals must be augmented in order for GbE signals to be transported.
Many optical networks are dense wave division multiplex (DWDM) based. DWDM-based networks may transmit data of substantially any protocol and any bit-rate. Hence, DWDM-based networks may transmit SONET, SDH, and Ethernet signals. FIG. 1 is a block diagram representation of a network. A network 100 may be a wide area network that includes a local area network 102 with nodes 110b-d and links 114a-d which allow nodes 110b-d to communicate. Nodes 110b-d may be network elements such as switches, while links 114a-d may be wireless communications links or wired communications links such as fiber-optic cable. A node 110a may be a client which requests access to nodes 110b-d through a trunk 118. Trunk 118 may be used to substantially interconnect nodes 110a-d to form network 110 from local area network 102 and node 110a. In other words, trunk 118 may be considered to be a communications channel between local area network 102 and client 110a. 
Local area network 102 may be a SONET/SDH network. As GbE is becoming more prevalent, the ability to carry GbE signals over local area network 102 that supports SONET/SDH is desirable. Hence, trunk 118 and node 110a may each include line cards which effectively allow GbE signals to be transported through network 100.
With reference to FIG. 2, line cards which are included in a client and a trunk will be described. A client 210 and a trunk 218 each include an add/drop multiplexer (ADM) line card 222a, 222b, a transponder line card 226a, 226b, and a muxponder line card 230a, 230b. ADM line cards 222a, 222b are arranged to provide an interface between higher speed and lower speed signals. By way of example, a SONET ADM may extract lower rate signals from a higher rate multiplexed signal or insert lower rate signals into a higher rate multiplexed signal. A signal may be added or dropped substantially without disrupting the transmission of other signals included in a multiplexed signal. Transponder line cards 226a, 226b function as transmitters and responders, and are arranged to pick up and to respond to incoming signals. Transponder line cards 226a, 226b are typically modules that receive an incoming signal and convert the incoming signal to a wavelength to be optically multiplexed with other wavelengths. Muxponder line cards 230a, 230b have the combined functionality of multiplexers and transponders, and are arranged to enable multiple channels to share a single wavelength.
Line cards associated with client 210 and line cards associated with trunk 218 are often different. For example, ADM line card 222a that is suitable for use as a part of client 210 may be different from ADM line card 222b that is suitable for use as part of trunk 218. For client 210, ADM line card 222a may be an ADM-on-a-blade line card.
With reference to FIG. 3, the steps associated with configuring a trunk or a client to support particular traffic types will be described. A process 300 of configuring a trunk or a client begins at step 304 in which a current traffic type that is to be transported across a SONET/SDH network is identified. Once the current traffic type is identified, transponder line cards, muxponder line cards, and ADM line cards that support the current traffic type may be purchased or otherwise obtained in step 308. Line cards are generally specific to line rates and protection schemes.
In step 312, the trunk or the client are configured to support the current traffic type. Configuring the trunk or the client often includes updating software associated with the trunk or the client. Then, the current traffic type is transported through the trunk or the client in step 316. A determination is made in step 320 as to whether a different, or unsupported traffic type, is requested. That is, it is determined if a different traffic demand has been requested. A different traffic demand may correspond to a different line rate, or a different protection scheme. If it is determined that a different traffic demand has not been requested, process flow returns to step 316 in which the current traffic type continues to be transported.
Alternatively, when the determination in step 320 is that a different traffic demand has been requested, then at least some of the line cards associated with the trunk or the client are replaced in step 324. In other words, new transponder line cards, muxponder line cards, and ADM line cards which support the different traffic demand may be purchased or otherwise obtained. Once obtained, the new line cards are installed in the system, i.e., the trunk or the client, and the system is configured to support the different traffic demand in step 328. After the system is configured to support the different traffic type, the different traffic type is transported as a current traffic type in step 322. From step 332, process flow returns to step 320 in which it is determined whether a different traffic type is requested.
Although replacing transponder line cards, muxponder line cards, and ADM line cards as necessary is effective in enabling new traffic demands to be supported, replacing line cards is inefficient. Having to replace one or more line cards, and to reconfigure an overall system once one or more line cards have been replaced, may be both time-consuming and expensive. Further, the use and the maintenance of multiple line cards is also often expensive.
While a network administrator may anticipate future traffic demands and configure a system accordingly, i.e., a network administrator may set up a system to support more than a set of initially demanded traffic types, future traffic demands are often difficult to predict. As a result, even line cards which account for future traffic demands are likely to have to be replaced when unanticipated traffic demands are requested.
Therefore, what is needed is a system in which different traffic demands may be supported substantially without requiring that one or more line cards be replaced. That is, what is desired is a method and an apparatus that has the flexibility to allow new traffic demands to be supported without the need for replacing line cards.